Author: Richard Pijl
Date: 14:48:00 05/27/04
Go up one level in this thread
>>>>>
>>>>>1)I asked the computer to print the moves in the book only to discover that
>>>>>printf("%s %s",move1,move2) does not work.
>>>>
>>>>Are move1 and move2 char* 's? If so, that should be fine.
>>>>What's happening?
>>>>
>>>>
>>>>--
>>>>James
>>>
>>>I do not know but for me it did not work and the computer printed the first
>>>string twice instead of printing 2 different strings.
>>>
>>>Try the following code that is part of movei:
>>>
>>>
>>>#define rankfrom(u) (((u)>>3)&7)
>>>#define rankto(u) (((u)>>9)&7)
>>>#define filefrom(u) ((u)&7)
>>>#define fileto(u) (((u)>>6)&7)
>>>#define promotion(u) ((u)&(1<<29))
>>>#define promote(u) (((u)>>16)&255)
>>>
>>>char *move_str(int move)
>>>{
>>> static char str[6];
>>>
>>> char c;
>>>
>>> if (promotion(move)) {
>>> switch (promote(move)) {
>>> case KNIGHT:
>>> c = 'n';
>>> break;
>>> case BISHOP:
>>> c = 'b';
>>> break;
>>> case ROOK:
>>> c = 'r';
>>> break;
>>> default:
>>> c = 'q';
>>> break;
>>> }
>>> sprintf(str, "%c%d%c%d%c",
>>> filefrom(move) + 'a',
>>> rankfrom(move)+1,
>>> fileto(move) + 'a',
>>> rankto(move)+1,
>>> c);
>>> }
>>> else
>>> {
>>> sprintf(str, "%c%d%c%d",
>>> filefrom(move) + 'a',
>>> rankfrom(move)+1,
>>> fileto(move) + 'a',
>>> rankto(move)+1);
>>> }
>>> return str;
>>>}
>>>
>>>printf("%s %s",move_str(1),move_str(0));
>>>
>>>//result b1a1 b1a1
>>>
>>>printf("%s %s",move_str(0),move_str(1));
>>>
>>>//result a1a1 a1a1
>>>
>>>Uri
>>
>>This is an easy one: your strings share one common place in memory, namely the
>>variable static char str[6]. Therefore when you call move_str() for the second
>>time, the first string gets overwrited.
>>Filip
>
>I do not understand why they share one place in memory.
>
>The computer is supposed to do the following:
>
>1)calculate move_str(0)
>2)forget every local varaible including str[6]
This one is a local 'static' variable. It keeps its value.
>3)calculate move_str(1)
This will overwrite str.
>4)forget every local varaible.
>
remember that an array variable is equivalent to a pointer in C. You're
returning a pointer to the array str, not the string itself.
return str;
is equivalent with
return &str[0];
>Note that it seems to do it in that way when I do it in 2 different printf for 2
>strings but not when I use one printf.
First both functions are called, and then the string is built by printf, so you
will get the same move twice.
Richard.
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